In recent years there has been an increasing number of surgeons using surgical staples, rather than conventional sutures. This is true because the use of surgical staples and surgical stapling instruments has made many difficult procedures much simpler. Of even more importance, however, is the fact that the use of surgical staples significantly reduces the time required for most procedures, and therefore reduces the length of time for which the patient must be maintained under anesthetic. Many types of surgical stapling instruments have been devised, for many different procedures. The present invention is directed to a linear surgical stapling instrument. This is an instrument which, in a single actuation, implants and forms at least one rectilinear row of surgical staples. Such instruments are used on many different organs and tissues such as the lung, esophagus, the stomach, the duodenum and throughout the intestinal tract.
In its earliest form, the linear surgical stapling instrument was a permanent, multi-use instrument and the surgical staples were manually loaded into the instrument one-by-one. An exemplary surgical stapling instrument of this type is taught in U.S. Pat. No. 3,080,564. While such instruments performed well, they were in general complex in construction, expensive to manufacture, heavy, bulky and difficult both to load with surgical staples and to clean and sterilize after each use.
The next significant improvement in linear surgical stapling instruments was the provision of presterilized, disposable loading units or staple cartridges. U.S. Pat. No. 3,275,211 and U.S. Pat. No. 3,589,589 are exemplary of those relating to permanent, multi-use linear instruments having replaceable staple cartridges. While this improvement significantly reduced the time previously required for hand loading of the staples, the basic instrument still had to be disassembled, cleaned, reassembled and sterilized for each procedure. Such instruments also frequently required maintenance and adjustment.
Even more recently, in view of rising hospital costs, there has been an ever increasing interest in disposable surgical stapling instruments to eliminate as much work as possible (i.e. disassembly, cleaning, reassembly, sterilization and the like) and to be more efficient, while at the same time not having to compromise the surgical procedures. U.S. Pat. No. 4,354,628 and U.S. Pat. No. 4,383,634, for example, each teach a disposable linear surgical stapling instrument. While devices of this sort perform well, since the forwardmost, anvil-carrying jaw is pivoted, the anvil and the cartridge do not approach each other in parallel relationship and only a single gap setting is achievable. In addition, it is sometimes difficult to properly position the tissue to be sutured within the jaws of an instrument of this design. Such instruments are frequently provided in a "tight" suturing version with short legged staples and a "loose" suturing version with staples having longer legs, the surgeon having to select the appropriate instrument for the particular procedure being performed.
The invention described in U. S. Pat. No. 4,527,724 provides a disposable linear surgical stapling instrument which is simple in construction and relatively inexpensive to manufacture. The instrument is characterized by a working gap or range of distances between the anvil and the cartridge over which a single size staple can be properly implanted and formed. The proper and desired setting of the instrument, within the working gap, is easily accomplished through simple manipulation of an adjustment knob at the rear of the instrument with indicator means on each side of the instrument to clearly show when the distance between the anvil and the cartridge is within the working gap. In addition, the gap to which the instrument is set can fall anywhere within the confines of the working gap of the instrument. The gap indicator is additionally designed to show at a glance whether the selected gap falls within the prior art so-called "tight" range or "loose" range.
The instrument of U.S. Pat. No. 4,527,724 is also provided with features normally associated with permanent, multi-use instruments only. The instrument, for example, has an alignment and retaining pin, shiftable to an operative position wherein perfect alignment between the anvil and the staple cartridge is assured, and wherein tissue to be sutured and located between these elements is maintained therebetween. The instrument is provided with a locknut device which precludes rotation of the adjustment knob to secure the desired gap, unless the alignment and retaining pin has been shifted to its operative position. The instrument is also provided with a novel trigger safety which will disable the trigger until the movable jaw of the instrument has been shifted to a position near the working gap. Latch means is also provided for the trigger, to secure the trigger with a snap engagement when the trigger is shifted to its fully actuated position, to give the surgeon a visual tactile and audible indication that the surgical staples have been properly and fully implanted and formed. For purposes of economy and simplicity, much of the instrument is made of appropriate plastic material, while all of the major load-bearing elements of the instrument are metallic. The instrument is so designed that the staple driver is coupled to the trigger at all times.
Nonetheless, the invention of U.S. Pat. No. 4,527,724 is deficient in certain aspects. Primarily, the mechanism used to adjust the staple cartridge from a large opening to a appropriate properly set gap requires manual screwing of a gap setting mechanism. What may be desirable is a fast closure device wherein, with one motion, the gap may be approximated, and then finally set. In addition, it may be desirable to have such an instrument with automatic retaining pin placement and return. In this system, it may further be desirable for the automatic pin placement and return to be coordinated with the closure mechanism such that feedback is given of whether there is an obstruction in front of the retaining pin or in front of the cartridge.
Of course, safety is always an issue and it would be desirable to have a mechanism wherein the firing of the mechanism takes place only within the range of a desirable pre-determined set gap. In some ways, it would be desirable to have a redundant mechanism where the security of safety is incorporated into the mechanism in two ways; first, a typical safety and second, the firing only within the appropriate range of set gap.